This invention relates to an oral adsorbent for adsorbing phosphate ions.
A phosphate ion adsorbent adsorbs or binds to the phosphoric acid delivered to intestines by the food containing the same, preventing the absorption of the acid in the body. With this activity, the phosphate ion adsorbent is orally administered chiefly to patients of hyperphosphatemia, renal insufficiency or the like. While a dried aluminum hydroxide gel has been conventionally used as an oral phosphate ion adsorbent, a long-term use of dried aluminum hydroxide gel results in the decomposition thereof due to the alkaline liquid in intestines, the gastric acid or the like, accumulating a large amount of Al ions produced in the body which cause dialysis encephalopathy, aluminum poisoning or the like.
In view of this problem, a calcium carbonate agent is currently used in place of dried aluminum hydroxide gel. However, this agent is also prone to decomposition owing to the gastric acid or the like which leads to production of a large amount of Ca ions liable to induce hypercalcemia. Further the agent is lower by about 20 to about 25% in the capacity of adsorbing phosphate ions than dried aluminum hydroxide gel.
Other various adsorbents are available but have problems in terms of the safety of human body and insufficient phosphate ion-adsorbing capacity.